v0: (initial public release)

v0.1:
  1. The button on the About.. form has been changed from "OK" to "Close".
  2. Add MARK option to Go To form.

v0.2:
  1. Caption on Current UT Time button changed to Current UT.
  2. Add "Context" help for errors loading JPL and texture files.

v0.3:
  1. Correct error in previous change -- context for Clementine was accidentally
     based on presence of USGS hi-res file.
  2. Load low resolution texture only if requested.
  3. Add "Save As Default"/ "Restore Defaults" buttons to Set Location Form 
     these save/restore both location and geocentric/topocentric choice.
  4. LTVT starts in Geocentric mode.
  5. Initial Sub-solar point is +90 (East).
  5. Detect when changes have been made in filenames or JPL path and
     (if so) prompt to Save new names (but not location) on exit.
  6. On Right-Click Go To, pre-fill form with Lon & Lat of mouse point -- this
     allows switching to Aerial View of current area.
v0.4:
  1. Delete (hidden) Aerial view button and right-click menu item.
  2. Add "Label" button to "Moon Display" panel and "Modify labels.."
     option under File... menu to change font and/or location.
  3. Add an "Add label..." option to the right-click mouse menu for annotating
     images.
  4. Changed NumericEdit unit to automatically substitute periods for commas in
     extended value entry boxes.
  5. Repaired JPL file boundary-crossing problem in MEP and PSS (they should
     both be able to silently cross making calculations using multiple JPL files
     as long as they are all in the a single directory.
  6. Corrected error in listing of librations in MEP and PSS -- longitude and
     latitude were formerly reversed.  Also corrected error in visibility code.
     It was indicating if Sun (not feature) was on visible disk.
  7. Suppressed MoonUp/SunDown symbol in both MEP and PSS when in geocentric mode
     and graying of lines for MoonDown in MEP.
  8. Completely re-wrote SunAngle search in MEP - it now does a brute force search
     using a user-specified interval defaulting to 60 minutes.
  9. Added option to filter output in MEP (suppressing lines that are not within
     the requested tolerance).

v0.5:
  1. Cross-hair cursor selection moved to top of right-click menu.  It is the only
     one that can have a check mark. Moved Add label... option up as well.
  2. Deleted "Clear Reference Point" as a separate option.  It now *replaces*
     "Set Reference Point" when the later is active and vice-versa.
  3. "Overlay Dots" and "Identify nearest feature" now check whether a newly-plotted
     dot is already in the CraterInfo array.  If so, a duplicate name is not
     added.  The penalty in time turned out to be minimal.
  4. Correct label for "Include feature size" checkbox on Modify Labels form --
     it was formerly chopped off.
  5. Back to Textures by default on startup.

v0.5:
  1. Delete unused "Measure Distances" option from right-click menu.

v0.6:
  1. Slight re-arrangement of order in right-click menu.
  2. MoonPosition unit has option to output Sub-observer and Sub-earth points in
     Mean Earth/Rotation axis system (formerly it was in the native Principal Axis
     System of the JPL ephemeris).  This system is offset from the PA system by
     three rotation angles, p1, p2 and tau.  Default values are provided but can
     be over-ridden by explicitly specifying these in the *.ini file.
  3. Add progress bar and "Drawing dots..." label while reading the Named Features File.
     Formerly program gave impression of freezing.

v0.7:
  1. Change name of principal axis to selenographic rotation angles in LTVT.ini
     file from MeanEarthAxis_p1Angle_arcsec to SelenographicAxes_p1Angle_arcsec etc.
  2. Use floating point (instead of integer) division to determine the pixel
     position in the reference map corresponding to 0 longitude and latitude.
     If the reference map contains an even number of pixels (0,0) will fall at
     a pixel boundary.  PDS Map-a-Planet, when it supplies grid lines, rounds down.
     LTVT shows (0,0) at the pixel boundary, which, at very high zoom will be
     at the lower right corner of the intersection of the PDS grid lines. If the
     reference map has a odd number of pixels, LTVT will show (0,0) in the center
     of the PDS lines.
  3. If an external file is in the LTVT.exe folder, strip the path from the file name
     before saving to the LTVT.ini file.
  4. Modify ExtendedValue routine in Win_Ops to replace commas with periods before
     trying to evaluate as a decimal number.

v0.8:
  1. Add file selection box for changing associations with external files.
  2. Correct error in Goto form where list in combo box was added to but not cleared on each showing.
  3. Move Save Image from File menu to button at lower right.
  4. Change Key names in LTVT.ini from  Low_Resolution_USGS_Relief_Map, Low_Resolution_USGS_Relief_Map,
     and Clementine_Texture_Map to Texture1_File, Texture2_File, and Texture3_File and
     at keys for radio button captions.

v0.9:
  1. FormClose dialog now has Yes-No-Cancel if file names were changed.
  2. File Associations form now has full path for all files.
  3. Change File... menu to Files...
  4. Move Moon Event Predictor from Tools... menu to button at lower right.
  5. Clean up file saving options in Save Image to make BMP the default (color
     is renedered more accurately) and eliminate .ico, .emf and .wmf options).
  6. Move Invert-LR, Invert-UD and BlackSky options to a new Display Options form
     under tools.
  7. PhotoSessionsSearch & MEP: add geocentric selection by checkbox.  Add more
     detail to printout.
  8. PSS file is now selectable through Change File Associations menu.
  9. PSS replaces semicolons with commas in .csv photo dates/times file.
 10. Move texture radio buttons to allow longer user-set captions.

v0.10:
  1. Remove compiler directives (of unknown origin) that appeared at top of
     this unit in Version 0.08.
  2. Modify Set Reference Point so that you don't need to Clear Reference Point
     before setting a new one -- when a reference point display is active,
     two options now appear:  Set New Reference Point and Clear Reference Point.

v0.11:
  1. Correct error:  SunRad was initially set to 1920 arc-sec instead of 1920/2,
     making terminator zone twice as wide as it should be unless updated by calculation.
  2. Introduce vector method of drawing terminator small circles, allowing rotation
     of line of cusps.
  3. Add optional overall rotation angle of image x-y axes (about z= towards observer),
     and optional cartographic mode in which central meridian of complete Moon image
     is vertical with north at top.
  4. Add checkbox to label options form to permit labeling satellite features by
     letter only.
  5. Add pop-up memo with calculation details; display controlled by checkbox on
     DisplayOptions form.
  6. Correct use of global variables in H_JPL_Ephemeris, so that when the JPL
     file is changed data from the former file will not be misinterpreted as
     currently valid data.

v0.12
  1. Change project and main unit names from LTVT_vn_nn to LTVT.  This allows
     the sub-forms to contain a reference to the main unit that does not
     need to be updated with each revision (e.g., for making declaration of
     FontLabel filename in main unit accessible to LabelFontSelector form).
     However, the .exe file now has to be manually tagged with the version number.
  2. Improve tool tips to explain more clearly that numeric longitudes are
     with E=+ and W=-; while latitudes are N=+ and S=-.
  3. Add ability to save font used for labeling maps (typeface, color, style,
     size and position) so it can be restored the next time the program is started.
  4. Add MouseOptions form. It gives control over cursor and three modes of
     readout with respect to reference point:
       a. Distance and bearing.
       b. Shadow length mode.
       c. Ray height mode.
  5. Change "Defaults" label on main screen to "Reset" to avoid confusion with
     other Save/Restore defaults buttons.
  6. Remove "crosshair cursor" and "clear reference point" options from right-click
     menu.
  7. "Display options" renamed "Cartographic Options".
  8. Add ability to display feature file containing Clementine altimeter data
     (code "AT") with point reading displayed as LIDAR elevation + revolution number.
  9. Add optional libration circle drawn when DOTS or TEXTURE is clicked.

v0.13
  1. Change cursor to hour-glass during lengthy operations.
  2. Add a trial version of options to calibrate and load user photos.
  3. Calibration data is stored in a sub-observer sub-solar + two user-defined points formats.
  4. Add an adjustable gamma function that can be used for altering the contrast/brightness of rendered textures.
  5. Note: this is a test version and was never publicly released.

v0.14
  1. Move original (X-Y center) boxes off main form to GoTo box. Completely rewrite
     all routines related to X-Y centering.  The screen X-Y system is identical to the
     selenographic Xi-Eta system if and *only* if one selects the Cartographic orientation
     mode with the Sub-observer point set to (0,0) and the rotation angle to 0.
     Under those circumstances, the Invert Up-Down, and Invert Left-Right options
     can be used without disturbing the X-Y (Xi-Eta) readout.  At all times and in all
     modes X-Y refer to the left-right up-down screen-oriented Cartesian coordinates
     of an image point the center of the system at the center of the lunar disk
     and the scale set so the lunar radius = 1 unit.
  2. The GoTo form now has radio buttons permitting it to operate either in the
     original longitude-latitude mode, or, now, in an X-Y mode.  The two modes
     operate in the same way, and offer the same options, with the exception that
     the X-Y mode can be used to specify a point off the lunar disk.  As before,
     the GoTo form can be accessed either from the Tools... menu or by right-clicking
     on the image.  When accessed by the right-click method, the form is pre-filled with
     the longitude, latitude and X-Y coordinates of the position at which the mouse was
     clicked.  Otherwise, it retains the last values entered.  Note: if the right click
     mouse position is off the lunar disk the longitude and latitude are undefined,
     so only the X-Y boxes are updated.
  3. Change "Personal Photo Calibrator" form to request photo date/time and observer
     location, rather than computed sub-observer and sub-solar coordinates;  the latter
     are automatically computed at Step 4 in the calibration procedure.  As a result
     the main LTVT form does not need to be set the photo date-time in order to
     determine the photo geometry.
  4. On the "Personal Photo Calibrator" form, the Save button is now visible *only*
     if the Step 4 radio button is clicked. Also, whenever the Save button is visible
     the current calibration can be previewed in the sense that the lunar longitude
     and latitude will be display below the image as the mouse is moved over it.
  5. Change format of saved calibration data to include not only the coordinates of
     the two calibration points and the sub-observer and sub-solar positions on which the
     calibration was based, but also the photo date, UT, observer location and image
     size in pixels.  At the moment the rendering of a calibrated photo is based entirely
     on the two calibration points and the sub-observer and sub-solar positions recorded
     in the calibration file, so this new information is used for display purposes only.
  6. Change name of user-supplied photo calibration data file.  The internal
     format is a North American-style .csv file (with periods for decimal points and
     commas for item separators) but the default file name will be PhotoCalibrationData.txt
     to prevent Windows from automatically opening it with a spreadsheet program.
     In many countries, the default .csv style is to use commas for decimal points
     and semi-colons for item separators.  In such countries, PhotoCalibrationData.txt can
     be successfully opened with the Microsoft Excel spreadsheet *only* if the user
     changes the Regional Settings preferences in the Control Panel to English(United States),
     but this is not recommended.  If changes must be made to  PhotoCalibrationData.txt,
     please do so with a simple text editor (such as Notepad or WordPad) retaining the simple
     text format.  LTVT will attempt to recognize files in the European-style, but this
     process can never be entirely reliable. LTVT records dates in the calibration
     file in the format YYYY/MM/DD.  LTVT *should* be able to read dates in the local
     national format, but placing dates in the calibration file in that format is
     **NOT** recommended, since such information is not exchangeable with users in other
     countries.
  7. Add a warning if the PhotoCalibrationData.txt file cannot be found and a new
     one is about to be created.
  8. For user-supplied photos, make the No_Data color user-selectable with a
     default of clAqua (cyan).  Selection is done in the Cartographic Options
     window.  Also add an option for drawing/not drawing the red and blue
     terminator lines.
  9. Update label information in saved LTVT images.  The default is now to specify
     the center of the image by longitude and latitude.  The center is given in
     terms of X-Y coordinates only if the center point is off the lunar disk
     (where longitude and latitude are undefined). Two additional lines have been
     added, one at the top and one at the bottom so that the labels once again
     include all information needed to recreate the image:  i.e., texture file
     name, inversion, rotation and orientation options.
     NOTE: .bmp (bitmap) format continues to be recommended for saved images.
     They can be easily converted to .jpg at a later time if desired.  LTVT does
     not do a good job of saving images directly to .jpg format (it can do it,
     if requested, but the quality is not as good as can be obtained by later
     conversion with a dedicated photo-processing program).
 10. The colors of the lines appearing at the top and bottom of the saved LTVT
     images may be selected in the Change Dot/Label Preferences... menu.
     NOTE: the last line, giving a date/time and observer location does not appear
     if the sub-observer location was changed since the last time the
     Compute Geometry button was clicked.  In such cases the main screen will
     say "Manually Set Geometry".  This applies, for example to *all* Aerial Views.
     In the saved images, a manually-set geometry is assumed unless otherwise
     indicated.
 11. Add capability for copying observer locations from a list on disk.  The name
     and location of the file are specified in the Change external file associations...
     menu (default = "Observatory_List.txt"). If a file of the specified name exists,
     the drop-down list is display, otherwise it is not.  The format of the file
     is a comma-delimited list consisting of East_longitude, North_latitude, Elevation (meters)
     and Name.  The Name is placed last so that it can contain any characters, including commas.
 12. In the Calibrated Photo Selector window, add readouts of all information found in the
     calibration disk file.  The locations and coordinates of the two calibration points are
     displayed in boxes allowing user modification.  If changes are made to the numbers in the boxes
     before clicking Select, those changes will affect *only* the current loading.  They do
     not in any way alter the calibration stored on disk.  Note that the Mirror code
     is a multiplication factor along the lunar X-axis.  The only two meaningful values are +1 and -1.
 13. In the Calibrated Photo Selector window, add two new checkboxes at the bottom
     of the form which allow one to "Overwrite geometry" and/or "Overwrite date/time/location"
     when a calibrated photo is selected.  The "Overwrite geometry" mode is the
     same as what was used in v0.13: that is, when the photo is loaded, the
     sub-observer and sub-solar points in the main LTVT window are set to those
     of the calibrated photo, the use "User texture" radio button is selected, and
     then the Texture button is clicked.  When "Overwrite date/time/location" is
     selected, those values will all be replaced in the main window, then the
     Compute Geometry and Texture buttons are clicked.  Assuming the calibration data
     have not been manually altered, the computation of geometry should yield the same
     sub-observer and sub-solar points as those stored in the file.  Hence both
     these options should photo as it was originally taken.  For example, if the
     original frame was entirely on the lunar disk, it should appear in as an
     undistorted rectangle (but probably rotated relative to the Moon's pole).
     If neither box is checked, then the photo is used as a texture, but drawn onto
     a globe with whatever geometry is currently set in the main window.  For example,
     if the Sub-observer point in the main window is set to (0,0), then the user-supplied
     photo will be drawn onto an unlibrated Moon.  This mode is useful, for example,
     for correcting photos from different days to a uniform geometry so they can be
     pasted together into a mosaic.
 14. Remove statement changing Set Ref Pt to Set New Ref Pt after first click.
 15. In Go To menu, "Mark" now re-sets the Ref Pt to specified value.  In Photo
     Calibrator form Ref Pt coordinates are copied.
 16. Improve dialog when new photo calibration file needs to be created, and add
     automatically generated header lines explaining the format.
 17. Better error messages and invalidate old user photo if an error is encountered
     reading the new calibration data.
 18. In cartographic options, add checkbox requesting LTVT to Compute Geometry with
     the current system UT at startup.

  v0.14.1 (mostly bug fixes)
    1. In Photo Calibrator, change notation for calibrated mouse readout from
       the "NP up" to the more informative "North pole up".
    2. Add Moon's angular diameter to information displayed in box in upper right
       corner of screen.  The value shown is two times the Arcsin of the Moon's
       radius, taken as 1737.4 km, divided by the distance from the observer's
       location to the Moon's center. At present it appears only in the topocentric
       mode.
    3. In Photo Calibrator: add warning message if one clicks on the image without
       having the Step 2 or Step 3 radio button clicked.
    4. In Main Program: ensure that if a brief file name (no path information)
       is found in the LTVT.ini file, the application directory, rather than the
       current working directory is assumed.
    5. Correct error : dot color of non-crater features was inadvertently
       hardwired to "Yellow" and ignored selection in Dot/Label Preferences window.
       It now honors the selection.
    6. Correct error : in saved images with manually-set geometry (e.g., aerial
       views) the line specifying the texture file name was overwriting the
       bottom part of the image.  It now prints in the proper location below
       the image.

  v0.14.2
    1. In Change Dot/Label Options provide a checkbox to include or not include
       annotation lines at the top and bottom of the saved images.  With the
       un-annotated images, it is easy to save a series that can be assembled,
       using a program like iMerge, into an arbitrarily large basemap for
       registering the frames of a mosaic.
    2. In Photo Calibrator, at Step 4, make visible a readout of the rotation
       angle of the raw image with respect to a standard north-up Moon, and
       also the Zoom needed in the LTVT main window to match the scale of the
       raw image.  These can be used to generate a mosaic basemap that matches
       the scale and orientation of the raw images.
    3. In the Calibrated Photo Selector form change the check boxes below the
       Select/Cancel buttons to radio buttons (only one can be selected at a time)
       and add two additional options:
         a. Load without changing main window geometry.
         b. Load at original scale and orientation.  This automatically sets the
         zoom and rotation angle of the LTVT main window to match the scale and
         orientation of the raw image.  To generate overlays corresponding to the
         raw images it is necessary then, only to select the desired reference
         map and click Texture (or Dots).
    4. Also in the Calibrated Photo Selector, add a line at the top that gives
       the full path to the currently selected image.  In the previous versions
       only the file name in the list box was visible, and there was no way to
       tell where it was located on the hard drive.
    5. Correct error: when a Dots Mode image was saved to disk, the name of the
       texture file was undefined. It is now set to "none (Dots Mode)".
    6. Add an "Inverse Shadow Length" elevation measuring mouse mode.  In this
       mode when a reference point is set at the tip of shadow a line is drawn
       back towards the Sun.  The mouse is moved back along the line until the
       shadow-casting bright pixel is encountered, at which point the readout
       indicates the elevation difference.  In the "normal" mode, the reference
       point is set at the shadow casting point and the mouse moved to the shadow
       tip.  The two modes should give identical results for any given pair of
       points.  Which mode is most useful depends on whether the thing one is
       most interested in is a feature in the ridge line or in the shadow line.
    7. Fix readout of Moon's apparent angular diameter so it can be displayed in
       Geocentric as well as Topocentric mode.  Notice that results are
       systematically smaller than JPL Horizons by about 0.1 arc second, and
       differ by a few minutes as to the time of apogee and perigee.
    8. In Dots Mode, make the colors of the Moon's sunlit and shadowed sides
       user selectable.  This is useful for creating transparent GIF mouse-over
       overlays for web presentations.  If the two colors are set to the same
       value then the background color can be chosen as the transparent color in
       a photo processing software, and the only the dots and label text will
       show in the overlay.

  v0.14.3
    1. Correct error:  "Marking" a point with the GoTo menu was corrupting the
       reference point.
    2. Correct error: in Mouse Options menu, last part of explanation of inverse
       shadow mode radio button was not visible.
    3. Clean up tab-order so that pressing TAB key moves through the buttons and
       input boxes in sequence.
    4. Add help on F1 feature:  when a button or input box is highlighted, pressing
       F1 will open and jump to the relevant section in the LTVT_UserGuide.chm
       file.
    5. In Photo Calibrator, add buttons to optionally change zoom of image being
       calibrated by steps of factors of 2.  The mouse location readout at the
       bottom of the screen continues to refer to pixel positions in the original
       image. If both the old and the new image, after changing the zoom, exceed
       the size of the viewing window, then the scroll bars are automatically
       adjusted to maintain the current centering.
    6. In Photo Calibrator, add additional safety checks to prevent completion
       of calibration with invalid data.  Specifically, do not attempt to
       complete calculation if the reference points are at the same location or
       at a longitude and latitude that cannot be seen in the current viewing
       geometry.
    7. In main program, add similar checks to avoid loading a user-calibrated
       image with invalid data.
    8. Add a work-around so that date/times prior to 1900 will print correctly
       despite faulty system date to string function.
    9. The GoTo...Mark... procedure formerly rejected points whose longitude and
       latitude placed them on the Moon's farside (in the current viewing geometry).
       It continues to issue a warning, but plots a red Mark showing the projected
       position (as if the Moon were transparent).
   10. Add a checkbox in the Files...Change External File Associations... menu
       for using an alternative method of copying internal texture bitmaps to the
       viewable window.  Tests by Paolo Amoroso found that the default method
       was incompatible with the Wine for Linux Windows emulator, but that this
       alternative method worked.  Also, removed range limits on the observation
       date input controls, which also caused problems with Wine.
   11. In Dot/Label Preferences, add a choice as to whether discontinued names
       (the ones in square brackets in the IAU list) should be included among
       those plotted.
   12. Add a right-click option to automatically label just the nearest dot.
       The dot is labeled exactly as if the Label button were clicked, but only
       a single dot is affected.
   13. Correct error:  In Change Dots/Label Preferences, when the default font
       was restored, the font sample was not being refreshed.  It is again.
   14. Correct error:  the "feature diameter" part of the Clementine Altimeter
       data listing is actually the satellite revolution number.  This was
       displaying properly in the mouse information area, but when labels
       "including feature diameter" were placed on the map, this value was
       erroneously listed as a size in "km".  The format of the map labels for
       both Clementine Altimeter and ULCN data points now match the form shown
       in the mouse information area.
   15. Change name of initial button on Photo Calibration page from "Load" to
       "Open".
   16. In Photo Calibrator add hour-glass cursor while large photos are being
       loaded.
   17. Correct error:  in Tools...Change Dot/Label preferences a positive Y-offset
       now moves the label up.  This was formerly reversed.

v0.15
  1. Change the way shadow lengths are interpreted when the User Texture
     button is selected. Formerly Earth-based photos were regarded as images
     of flattened spheres on which accurate selenographic longitudes could be
     inferred from the X-Y position.  Now they are regarded as projected images
     of features seen in relief.  The position (x1, y1) of point P1 at one end of
     a shadow segment is turned into a vector V1 representing its position
     in three dimensions relative to the center of a selenographic sphere of
     radius R0.  A line is then followed in the projected direction of the
     solar rays to find the (x2, y2) projected position of the other end.
     Starting at point P1, a vector, S, in the direction of the solar rays is
     traced until its projected tip is at (x2, y2).  The sum of V1 + S is a
     vector with its origin at the center of the sphere representing the
     3-dimensional position of point P2 at the far end of the shadow segment.
     The difference in length of V1 vs. V2 is taken as the difference in
     elevation. This method should give accurate elevation differences, although
     when analyzing Earth-based photos, there will continue to be small errors
     in longitude and latitude because the actual topographic features are
     seen somewhat displaced (radially) by projection from the positions they
     would have on a constant radius sphere.
  2. The method of calculating the heights of the minimum and maximum rays above
     or below the lunar surface in the region beyond a shadow casting peak has
     not yet been adapted to the user-supplied photo mode.  A warning is issued
     if one closes the Mouse Options form with this option selected while a
     user-supplied (Earth-based) photo is being displayed.
  3. Add capability to display dot file with Kurt Fisher's list of crater
     depths.  Code "CD" is used to designate items of this type.

v0.16
  1. Rework the convention for Feature Size Threshold to allow plotting data from
     lists where some entries contain Size entries that cannot be interpreted as
     numbers (e.g., blank or non-numerical codes).  The meaning of the Feature
     Size Threshold is now as follows:
       a. Feature Size Threshold = -1 : display all features flagged by
         a non-blank entry in the first column.
       b. Feature Size Threshold =  0 : display all features in the list.
       c. All other values:  display an entry if and only if the "Feature Size"
          field can be successfully decoded as a number and that number equals
          or exceeds the specified threshold.
  2. Modify the CalibratedPhotoSelection form so that pressing the ENTER key
     is equivalent to clicking on the Select button (i.e., it loads the currently
     highlighted photo with the current radio-button selection).  This makes
     it possible to select a previously calibrated photo entirely with the keyboard
     (up-down arrows to highlight; ENTER to select).
  3. Add display to GoTo longitude/latitude window so it indicates the Rkl and
     LTO map numbers in which that point lies.
  4. Change Earth-based elevation difference readout to be consistent with
     older method: difference is now always mouse point elevation with respect
     to reference point elevation.
  5. In Dot/Label Options form, move and rename checkbox regarding inclusion/exclusion
     of IAU discontinued names from the Label Options group to the Dot Options group,
     since it determines whether dots will be plotted.
  6. Also in the Label Options group of the Dot/Label Options form add checkboxes
     to include/not include the feature name and the units of the feature
     dimension.  One can now independently pick and choose which elements one
     wants in the label:  name and/or size.  For satellite features, the name
     can include or not include the name of the parent feature (in addition to
     the satellite letter). For sizes, the label can include or not include the
     units.  If you lists both a name and size, the size is shown in parenthesis.
     If on the size is given, then no parenthesis are used.
  7. Change logic of labeling to label feature sizes using the literal entry in
     listed in the disk file (formerly the size entry was converted to a number
     and then formatted back to text with a fixed precision).  This permits
     non-numeric size entries:  for example, "3x10" or "approx. 5" for the
     diameter of an irregular crater.
  8. Under Files... menu on main page, add an option for viewing and loading into
     the main window Lunar Topographic Orthophotomap (LTO) and Topophotomap image
     files from the Lunar and Planetary Institute website.

  v0.16.1
    1. Modify key trapping so that when either the PhotoCalibrator,
       MoonEventPredictor, PhotoSessionsSearch, or LTO_Viewer sub=programs are
       running, the keystroke combination CTRL-TAB will switch between those windows
       and the main LTVT window.
    2. Modify User Photo Calibrator to save Sub-solar longitude as a value between
       -180 and +180 degrees.
    3. Modify texture radio button labels so they appear black if and only if
       the texture has been loaded. If the texture has not yet been loaded, the
       label appears gray.
    4. Correct errors involving left-right and up-down inversions when user-calibrated
       photos are loaded in original geometry.  Formerly, these were not properly
       initialized, and mirror-reversed images might appear in a non-reversed
       window.
    5. Add a checkbox to the GoTo window which (if checked) restricts the items
       listed in the drop-down box to the specially flagged features in the
       current dot file that display when the Feature Size Threshold is set to -1
       (flagged features have a non-null character in the first field).  The
       status of this box is *not* saved or restored with the other program options,
       but it *is* automatically checked when one first loads either
       "ClementineAltimeterData.csv" or "2005_ULCN.csv".  In the former case,
       no items are flagged, so the drop-down box is blank.  In the latter case,
       control points carried over from the 1994 ULCN are flagged, and so they
       appear in the drop-down box.  To see all the points in the dot file, one
       has to manually uncheck this box, close the form, and then re-open it.
    6. Add hour-glass cursor while GoTo window drop-down list is being prepared.
    7. In the dot files, add feature type category "GD" for GLR dome catalog features.
       These are treated the same as satellite craters (code "SF"). The only difference
       is the mouse display identifies them as "Dome" rather than "Crater".
    8. Modify implementation of Kurt Fisher's "CD" code for crater depth. It now
       works like "SF" and "GD" and the unit is correctly shown as "km" (it was
       formerly given incorrectly as "m").
    9. Modify the dot/label preferences form so that the dividing points between
       craters of various sizes can be set to non-integer values.  This permits,
       for example, Kurt's crater depths to be color=coded by fraction of a kilometer.
   10. Update default time span in MoonEventPredictor from 2006-2007 to 2007-2008.

  v0.16.2  (not publicly released)
    1. Correct error: since adding the Linux Compatibility mode it has not been
       possible to set the year to dates before 1758, because (for Linux
       compatibility) no minimum date was assigned to the date controls.  The
       minimum date is now set at runtime to 1/1/1600 if Linux Compatibility
       has not been requested, and the Set Year window works again.
    2. Correct error:  starting in v0.16, the option to exclude discontinued
       features was being ignored when the feature size threshold was set to zero.

v0.17
  1. Correct error: when a dot was added by the Right-click Identify Nearest Feature
     option, the feature size did not display.
  2. Correct "Flagged Features Only" checkbox in GoTo form so that the list in
     the drop-down box is updated immediately upon changing the check mark.
     Previously one had to close and reopen the window to see the updated list.
  3. Move Additional Rotation Angle box from Cartographic Options to Moon Display
     section of Main Window, and add an input box to request a latitude/longitude
     grid.  The grid is drawn if and only if the box is set to a non-zero value.
  4. Also in the Moon Display section of Main Window, add a check box to request
     that circles corresponding to the feature size be drawn around each dot.
  5. In Dot/Label Options, add user-selectable color fields for plus mark used
     to Mark and show Reference Points, and for the option feature size circles.
  6. Check if Texture File buttons in Moon Display window need to be grayed out
     when Restore Defaults is selected in External File Associations window.
     Formerly a change was detected only when a file name was manually changed.
  7. Improve handling of ULCN dots:
     a. For 1994 ULCN (feature type code 'CN'), show control point code number
        if a common name is not available.  Formerly these names appeared blank
        in the labels and GoTo box.
     b. For 2005 ULCN (feature type code 'CN5'), show expected error ("EVP") of
        height estimates in the mouse readout.
     c. For both files, display the numeric set number (1-5) of the dot in the
        mouse readout area.
  8. Add feature type codes CN and CN5 to the list of types to which the three-level
     coloring scheme in Dot/Label Preferences applies.  This feature can now be
     used for coloring the control network dots according to elevation zone (e.g.,
     <1735, 1735-1737, and >1737 km).  The complete set of codes to which the
     scheme is applied is now: AA, SF, CN, CN5, GD, and CD.  Clementine altimeter
     data cannot be sorted in this way because the elevation data is in the name
     field rather than in the dimension field of the dot file.
  9. Begin to add ability to load LAC charts (not yet fully implemented).

  v0.17.1
    1. For images saved in JPEG format, change compression setting from 100 (max)
       to 90.  This produces files are indistinguishable, but half the size
       (approx. 180 vs. 360 kb).  It is still recommended that files be saved
       in the BMP format, and that a third party image viewer (such as Photoshop)
       be used to convert them to JPEG. The results are sharper and the colors
       cleaner than a JPEG saved directly from LTVT.
    2. Complete implementation of mechanism for loading LAC maps (from Lunar
       and Planetary Institute website) in Mercator and Lambert Conformal Conic
       projections.

  v0.17.2
    1. When a dot is added by right-clicking and requesting "Identify nearest
       named feature", the dot is plotted using the current reference point color.
       Formerly the dot was always plotted in aqua (cyan) with no choice. It is
       also drawn as a circle with the diameter specified in the Dot/Label
       Preferences window.  Formerly it was drawn as a 2-pixel square.

v0.18
  1. Remove "Select" button from GoTo box.  It served no purpose and was
     confusing.
  2. Move controls in Photo Calibrator from left side to right, and make form
     resizable.  As the window is resized, the image expands to the lower
     right.
  3. Introduce convention in Photo Calibrator form that an observer elevation
     of -999 is taken to mean that the preceding longitude-latitude are the
     sub-observer point on the Moon rather than the observer's location on
     Earth.  This permits the loading of orthographic map imagery (where the
     sub-observer point is effectively lon=0/lat=0).
  4. Make a near-clone of the (user) Photo Calibrator for calibrating narrow
     field, near-normal satellite photos.  It is accessed through a "Calibrate
     a satellite photo..." option under Files... in the main window.  Satellite
     photos will initially be treated on the assumption that they are identical
     to the orthographic view that would be obtained from over an effective
     sub-observer point obtained by drawing a line from the Moon's center parallel
     to the line of sight, i.e., that they are equivalent to the view obtained
     from the same direction but at a great distance. In addition to the two
     reference points, the data required are the longitude, latitude ("nadir")
     and elevation of the satellite, and the longitude and latitude of the
     principal ground point (intersection of line of sight with lunar surface).
     Satellite photo calibration data are intermingled with the user photo
     calibrations, but identified by a new code "U1" indicating the special
     meaning of the long/lat/elev as a satellite position rather than an observer
     location on earth.
  5. Add right-click mouse option to set reference point on nearest dot.  This
     permits precise copying of dot coordinates without having to zoom in on dot.
     It can be used, for example, to set the reference point to the exact
     position of a ULCN control point.
  5. Add right-click mouse Help option to bring up page in Help File explaining
     each right-click option.

v0.19
  1. In Calibrated Photo selection form, add option to filter list based on
     a specified longitude and latitude.  When that option is checked, the
     program checks each calibrated photo and displays only those for which
     the specified longitude and latitude falls within the calibrated pixel
     range.  In addition each listing is preceded by the Sun's altitude and
     azimuth at that position based on the date/time associated with the photo.
  2. Also in the Calibrated Photo selection form, add a SORT checkbox.  If
     this is checked, then when one clicks "List Photos" the available items are
     listed alphabetically (in the feature search mode, in order of descending
     sun angle).  If the box is not checked, the items are listed in the order
     in which they are encountered in the CalibratedPhotos data file. When one
     changes from one display mode to another, LTVT attempts to highlight the
     last selected photo based on the file name.
  3. Also in the Calibrated Photo selection form, add a CHANGE button to permit
     changing the file of calibration data that is searched without having to
     go to the "Files...Change external file associations..." menu.
  4. In the Photo Session Search form, add similar button to permit changing
     the file (of photo date/times) being searched without having to go to the
     "Files...Change external file associations..." menu.
  5. In the Tools... and right-click menus, add a circle drawing tool.  It draws
     a circle (ellipse as seen in projection) of the specified diameter at
     the specified location.  Its intended purpose is to permit more accurate
     estimates of the size and location of lunar features.  Like the GoTo
     window, if invoked by a right-click, the longitude/latitude boxes are
     pre-set to the current mouse position.  If invoked through the Tools...
     menu, the control reappears with the longitude/latitude boxes unchanged.
     The numeric values in the input boxes can be incremented with the UP-DOWN
     arrows on the keyboard.  In that mode, the step is approximately 1 pixel
     per keystroke.  Holding down the SHIFT key increases the step by 5X.
     The center of the circle is indicated by a plus mark.
  6. Make size of plus marks (used for representing reference points, center of
     circles drawn with Circle Tool, etc.) adjustable by via Dot Size input
     box in Dot/Label Options window.  The plus mark generated by the circle
     drawing tool is drawn at the current Dot Size.  All other plus marks are
     drawn at the (DotSize + 1).  Setting Dot Size to -1 or less will suppress
     the drawing of the plus mark at the center of a circle generated by the
     Circle Tool. Reference Marks will not be visible if the Dot Size is -2 or
     less. The center mark generated by the Circle Tool can also be suppressed
     by unchecking the "Show Center" checkbox on that form.
  7. In the X-Y section of the GoTo form, add a Redraw button.  This refreshes
     the main image (re-centers on specified X-Y) without having to close the
     window.  The X-Y values can be incremented or decremented using the
     UP-DOWN arrows on the keyboard.  In that mode, the step is approximately 1 pixel
     per clikeystroke ck.  Holding down the SHIFT key increases the step by 5X.
     This allows the images in two copies of LTVT (running simultaneously) to
     be accurately aligned.  This is most easily accomplished by the following
     procedure: (a) left-click on the feature on wants to be the center in one
     image; (b) right-click on the same feature in the second image and select
     GoTo... from the pop-up menu; (c) select the X-Y mode and click REDRAW --
     this will center the image on the desired feature; (d) click on the X-value
     data entry box and use the UP-DOWN arrow keys to optimize the value; (e)
     repeat with the Y-value data entry box.
  8. Change default date in LTVT main window from Dec. 31 2006 to Dec. 31 2007.
  9. Correct error in drawing of plus marks.  Formerly they were unsymmetric about
     the central point, with the arms at the top and left missing one pixel at the
     end.
 10. Modify the Change Location window so that if a drop-down list of Observatory
     Locations is being used, and the current location matches one, the name of
     that listing will appear as the current selection in the combo box.
 11. Improve algorithm for checking calibration in Step 4 of the Satellite Photo
     Calibration form.  As the mouse is moved over the image, LTVT solves for
     the projection of the current pixel onto the lunar sphere and correctly
     displays the longitude and latitude at which that pixel will appear in the
     LTVT main window.
 12. Modify the scheme for shadow measurements on user-calibrated photos in the
     following ways:
       (1) In Cartographic Options window, add data entry box for specifying
         length of red line drawn during making shadow length measurements.
       (2) In effect, draw red lines based on the expected pixel positions of
         a straight line in the direction of the projected sunlight in the
         original image.  This may or may not appear as a straight line in the
         LTVT main window, depending on the geometry to which the image is mapped.
       (3) As the mouse is moved along the red line in LTVT main window, the
         shadow calculation is based on the corresponding position along the
         straight line in the original image.
     As a result of these changes, consistent and accurate elevation differences
     can be determined on the basis of shadow lengths independent of the projection
     in which the image is displayed.  This means the sunlight direction in
     LTVT-projected satellite images is now correct (it was formerly only approximately
     right) and the elevation differences are rigorously correct even with the
     close range perspective of the original.

  v0.19.1
    1. In Calibrated Photo Selection form, add option to overwrite sub-solar
       position only.
    2. In Calibrated Photo Selection form, change filename sorting to a case-
       insensitive mode.
    3. Modify Circle Drawing Tool: (1) "Draw" button is highlighted each time
       form opens; (2) can use ESC key to close form.
    4. In Moon Event Predictor, reset date/time format each time form is opened.
       For unknown reasons, UT time listings would switch to am/pm format.
    5. Move what was formerly "PhotoSessionsSearch" to Files... menu as
       "Search a photo times list...".  This can still be used for searching
       a list of the dates/times of uncalibrated photos.
    6. Rename button in lower right to "Find Photos": clicking it is now the same
       as the "Files...Load a calibrated photo..." function in the main menu,
       except that in the Calibrated Photo Selection form the "Sort" and "Filter"
       boxes are automatically checked, so one sees a list of *only* those
       calibrated photos containing the center point of the present LTVT image.
    7. Add a "Save Image" choice to the options available under "Files..." in
       the main window.  It is identical to clicking the "Save Image" button
       in the lower right of the screen.  The menu option allows the current
       LTVT screenshot to be saved to disk by the keystroke combination:
       ALT-F-I.
    8. In "Change Cartographic Options" form, change default orientation to
       "Lunar Atlas".  With the new photo-searching capability, this works
       better than the alternative ("Line of Cusps") mode when a new view of
       a given scene is loaded, especially with the "Overwrite sun angle" option.
       In the "Lunar Atlas" (central meridian vertical) mode, the existing scene
       is repainted with the new photo and only the sun angle readout is affected.
       In the "Line of Cusps" vertical mode, the new image has to be rotated
       compared to the old one, which can cause the object of interest to shift
       out of the viewing window.
    9. Correct Calibrated Photo Selection form so it won't attempt to sort a
       list containing less than two entries.
   10. Improve error trapping if calibrated photo list contains invalid/non-
       numerical data.

  v0.19.2
    1. Slightly increase blank space on left and bottom to try to avoid program
       window being placed in scroll bars on Windows desktops with newer "themes".
       Note: LTVT was designed on a Windows XP system with the "desktop theme"
       set to "Windows Classic" (simple square windows without fancy 3D effects).
       It will look best on a system set the same way.
    2. Add checkbox to automatically mark center pixel of image.  This is useful
       for making small changes to the centering. The mark is a plus mark drawn
       with the current Reference Mark options.
    3. In the GoTo menu, using the Up-Down arrows to modify the X-Y values shifted
       the image by 1 pixel or 5 pixels (with SHIFT key held down).  Change this
       to 3 pixels with SHIFT, 9 pixels with CTRL, and 27 pixels with both.
    4. When a calibrated photo is loaded, indicate in the main window that the
       geometry has been manually set (based on the values in the calibrated
       photo database listing) unless it has actually been re-computed based on
       the displayed date/time and observer location.
    5. Add "Libration Tabulator" to the Tools menu.
    6. In "Change External Files" permit Texture 3 to be a cylindrical projection
       texture file covering less than the whole sphere.
    7. Increase Percent Illumination display in upper right of main window from
       2 to 3 decimal points.  This is only a theoretical value, but the extra
       precision helps to distinguish small differences near New and Full phases.
    8. Remove the "Tools...Set year..." function.  That dialog box is now accessed
       by pressing the ESC key while a date setting date-time box has focus.
       It can now be invoked in this way for ALL date-setting boxes on all forms.
       Also change the functionality so that it overwrites the year but preserves
       the month and day (previously these were reset to "1").
    9. In external files selection dialog, change filter for Lunar Features
       (dot) file and Photo Sessions Search file to include *.txt as well as
       *.csv.
   10. Add "RECORD" button to the Circle Drawing Tool that automatically writes
       the current diameter and position to a dot file called "CircleList.txt"
       in the application directory.  If a file of that name already exists, the
       new data is appended to it.  Otherwise the file is created.
   11. Add button to Satellite Photo Calibrator form to automatically copy
       Clementine support data from *.LBL file, if it can be found.
   12. On start-up, encode date box on main page to Dec. 31 of current year.
       In earlier releases it was permanently set to 2006 or 2007.
   13. Correct error causing red shadow-measuring line to be drawn in wrong
       direction on user photos displayed with left-right inverted.
   14. Remove inadvertent "2020" Max Date restriction on date input boxes in
       Moon Event Predictor.    
   15. Correct error in column headers newly created photo calibration files.
       The labels for the columns containing X-Y pixel positions and lunar
       lon-lat were inverted.  Calibration data is listed in the order: "X-pixel,
       Y-pixel, Longitude, Latitude".  The header comments are for reference
       only and do not affect the operation of the program.

  v0.19.3
    1. In PhotoSelector, artificially set Alt/Ax of Sun to 90/0 for images with
       observer elevation of "-999".  This puts all maps in a separate category
       at the top.  Also add option to show librations in longitude and latitude
       in the selection list (these do not affect the sequence in which the
       photos will be sorted).
    2. Slightly reformat the Calibrated Photo Selection menu to give more space
       for wider borders.  Slightly reduce the height of the list box to permit
       inserting a header line at the top identifying the column contents. Also,
       when the "Filter" option is selected, add text after the header line that
       gives the sun angle at the selected feature using the Subsolar Point in
       the main window; and the X-Y position of the feature in the currently
       selected photo.  X is the position expressed as a fraction of the photo
       width starting from the left.  Y is fraction of the photo height measuring
       down from the top. The location of the feature is also indicated by a
       plus mark drawn over the thumbnail image.  The plus mark is drawn with
       the same style and color as the current reference mark.
    3. To Tools... add temporary function to superimpose rectangles representing
       the Rkl map zones using the Grid color. Since the lines are drawn in
       apparent Xi-Eta, this is accurate only in zero libration views.  Dashed
       centerlines are added (dividing the zones into subquadrants) depending on
       the status of the Rkl panel in the GoTo menu.  Dashed lines are added
       if a quadrant is selected.  They are omitted if "Center" is chosen.  This
       determines the grid style whether or not a GoTo action has actually been
       performed.
    4. In Right Click menu add option to record shadow length measurement.  This
       option appears only when the Mouse Option is set to Direct or Inverse
       Shadow Length Measurement. The result is written to a disk file if and
       only if such a file exists and has been initialized with the Circle Drawing
       Tool.
    5. In the Dot/Label Preferences menu add a checkbox requesting that when a
       shadow measurement is recorded the plotted position will be projected to
       its position on a constant radius sphere.  This shows the relation between
       the reference point and the measurement point in a plan view.
    6. In the Circle Drawing Tool add a button to initialize a file for holding
       the shadow measurements.  If the file exists and has been initialized
       since LTVT was started, selecting the Right Click option to record a
       shadow measurement will both write it on the image and record the result
       to the disk file.  This includes the distance of the shadow point from
       the center of the circle at the time the file was initialized. Only one
       copy of LTVT can use the file properly at a time.
    7. In the Dot/Label Preferences menu add a checkbox requesting that for
       satellite feature letters, the value in the horizontal box be used as
       a radial offset towards the parent feature. The letter is printed in the
       direction towards the parent feature by the amount in the horizontal
       offset box plus one-half the font size.  This has no effect except in
       connection with satellite feature letters where the parent name is omitted.
    8. In the GoTo menu, add a panel that can Go To the longitude and latitude of
       the center of a Rkl map zone (or a subquadrant of one).  In a few cases
       at the limb the latitude and longitude are not defined.  In that case the
       image is centered on the nominal X-Y position of that zone, which gives
       a valid result only for zero-libration views in atlas orientation with
       zero rotation (it /does/ handle left-right and up-down inversions correctly
       in all cases).  The Rkl zone GoTo has an auto-plot option which (if checked)
       goes through the steps needed for generating WikiSpaces Rkl maps -- that
       is, adding the Rkl grid, overlaying and labeling the dots with the
       current dot and label preferences.
    9. In the About form, add link to LTVT Wiki web address and automatically
       update the copyright end date to the current year.

  v0.19.4
    1. Change Location Selector box to Auto-Dropdown mode to give it same look
       and feel as the Feature Name Selector box in the GoTo menu.
    2. Add warning box if one attempts to superimpose Rkl grid with Sub-Observer
       point set to anything other than (0,0).
    3. Internally change vector format in all units from MVectors to MPVectors.
    4. In PhotoSelector, add button to copy image info to clipboard for purpose
       of building image credits for map pages on the-Moon Wiki (this control is
       not normally visible at run time).  Also correct coding so that geometry
       readout on main form is not set to "Manual" if the "overwrite none" option
       is selected for loading a photo.
    5. Add a function to extract a feature's parent name based on USGS feature
       type code, and to Right-Click menu add an option to identify and label
       nearest feature plus all features sharing same parent.
    6. To Cartographic Options form, add options to display Moon simulations in
       equatorial and alt-az orientations. A warning is issued if the information
       needed to do this does not seem to be current.

  v0.19.5
    1. Read Feature List from disk to memory and update only as needed.
    2. Update GoTo list only as needed.
    3. Change caption of "Change Location" button in main window to
       "Location".
    4. Add status info to Mouse Display box caption that identifies orientation
       mode of current map.
    5. Add warning if shadow measurements are attempted using a user photo
       drawn with a subsolar point differing from the one encoded in the
       calibration data by more than 0.01 deg, and if so, offer to transfer
       the subsolar point data from current photo calibration info to the
       boxes in the Main Screen and redraw the texture.

  v0.19.6
    1. To Tools, add "Show Earth viewed from Moon".  This shows, in the main
       window, a north-up image of the Earth centered on the point from which
       the Moon is at the zenith.  The gamma can be adjusted, but not the zoom,
       rotation, centering or orientation.  Most of the Right-click Menu items
       are hidden, as are the "Center On" and "Aerial Image" buttons in the GoTo
       box.
    2. Add Earth texture to External File Associations menu.
    3. Revise labeling of Saved Images to be sure to give date and/or location
       on which Equatorial and Alt-Az orientations are based.
    4. Change default sky color to "Navy" (dark blue).

  v0.19.7
    1. Move routines for determining map zone from GoTo form to a separate unit.
    2. Correct error in assignment of Rkl zone for features in the small limb
       areas that fall outside the normal Rkl rectangles.
    3. Add continuous readout of map location to caption of Mouse Position
       readout box in main screen.  If the current mouse location can be
       converted to a valid selenographic longitude and latitude, this will
       include the IAU format LAC/LTO zone and if the feature is on the
       Earth-facing hemisphere it will be followed by the Rkl zone denoted
       R1..R76.
    4. Add libration readout to information in Mouse Position box when in Earth
       Viewer mode.
    5. Correct hints for information lines in Mouse Position box so they change
       depending on the display mode (Earth vs. Moon images).
    6. Add to Tools menu an option to draw circle representing limb as seen by
       currently specified observer at currently specified time.  This is
       accomplished by setting the appropriate values in the Circle Drawing Tool
       and clicking the "Draw" button, so the color will be whatever is specified
       there. This option has to be used with caution because there is no
       guarantee the specified time and location correspond to the desired
       observer.
    7. Corrected variable MoonRadius, used in some distance calculations, from
       1738 to 1737.4 (formerly used only in angular diameter calculations).
    8. In Cartographic Options form, change caption of check box from "Show
       libration circle" to "Show mean limb".
    9. Modify GoTo form hints and visibility of controls to change between
       Earth and Moon viewing modes. Delete obsolete/erroneous hint saying Mark
       button set reference point.

  v0.19.7.1
    1. 11/28/08: Correct duplicate variable introduced in v0.19.6 which produced
       erroneous interactive mouseover sun angle readout based on last
       mouseover computed subsolar point in Earth Viewer.  Corrected lines in
       both v0.19.6 and v0.19.7 files on LTVT website.

  v0.19.8
    1. Suppress drawing of circles for dot features whose numeric data is an
       elevation, specifically USGS Codes AT, CN, CN5 and CD.
    2. Add start/end option to libration tabulator. When checked, the listing
       gives the start and end times of the intervals meeting the criteria.
    3. Fix cycling between forms with CTRL-TAB. In old scheme, forms were
       prioritized and, due to a typo, cycling from the Libration Tabulator to
       the Main Window returned to the Moon Event Predictor.  Under new scheme,
       CTRL-TAB in Main Window will always cycle to the last form, if any, from
       which the Main Window was accessed with CTRL-TAB. If the Main Window has
       not previously been accessed by CTRL-TAB, it will cycle to the first open
       form, if any, using the old prioritized list.
    4. Add checkbox to PhotoSelector form permitting calibrated photos to be
       listed in order of ascending colongitude instead of descending solar
       altitude.
    5. Delete display of word "Clementine" in mouseover display of altimeter
       data with feature type code "AT", since altimeter results from other
       missions, such as Kaguya, are becoming available.
    6. Add an Abort button to the PhotoSesssions and Moon Event Predictor
       search forms.   
    7. In Libration Tabulator, hide MinMoon and MaxSun elevation input boxes
       when geocentric mode is selected; and correct operation so that the
       calculated geocentric "elevations" of the Moon and Sun are ignored.
       In previous version, some valid date/times may have been rejected based
       on meaningless calculations of geocentric elevations.
    8. Add printout of current constraints in header at top of Libration
       Tabulator listings.

   v0.19.9
    1. Enlarge Calibrated Photo Selection form horizontally, and rearrange
       buttons at top of memo area for improved functionality with respect to
       colongitude, which can now be displayed independent of whether list is
       filtered or not.  Sort by: (1) colongitude if that checkbox is checked;
       (2) solar altitude if list is filtered AND colongitude not checked;
       (3) otherwise, by filename.

  v0.19.10
    1. In Moon Event Predictor, correct inadvertent error introduced when Abort
       button was added.  This forced user to exit and restart program to
       erase the Abort request.
    2. Also in Moon Event Predictor, when Geocentric Observer box is checked,
       replace display of Moon and Sun altitude and azimuth (meaningless for
       such an observer) with traditional estimates of Moon's phase at time of
       event: elongation, percent illumination and "age" (days since last New
       Moon).
    3. Finally, when the Moon Event Predictor button was clicked, the Sun angle
       and azimuth at the image center point were recalculated based on the date
       and time displayed in the main window .  They are now determined based on
       the sub-solar point displayed in the input boxes in the upper right of
       the main window. These may differ from those corresponding to the currently
       displayed date and time since they can be altered by manual entry or by
       loading a calibrated photo.  As before, the current date and time is
       copied from the main window, which makes it possible (if desired) to
       update the search data by clicking the "Calculate" button in the Moon Event
       Predictor form.
    4. In the Moon Event Predictor, Libration Tabulator and PhotoSessions Search
       forms, upgrade the user location selection box to include the drop-down list
       of observatory locations
    5. Add an "Add" button to each user location selection box.  This will append
       the current location to the current list on disk (if one exists) or create
       one with that location (if it does not) using the current text in the drop-
       down box as the site name. The drop-down box is now present at all times,
       whether or not a list currently exists on disk.
    6. Correct longstanding potential error in Moon Event Predictor : when
       filtering on sun azimuths, similar values near due north, such as 1 deg
       and 359 deg were being suppressed because of the large absolute difference.
       Before testing, the difference between the actual and target values is now
       reduced to an angle in the range +/-180, with a maximum possible absolute
       error of 180 deg. With the new logic, filtering on "-90 deg" is the same
       as filtering on "+270 deg", which it was not, formerly.  Also, make sure 
       print color is returned to black after using the gray font.
 
  v0.19.10.1
    1. Modify action of "Add" button in Observer Location boxes. Version 0.19.10
       attempted to copy the name from the drop-down box, but entering text similar
       to existing text changed the data in the longitude/latitude boxes.  Now
       clicking "Add" brings up a separate form for entering the new name.
    2. Modify comparison with existing data of text entered in Observer Location
       boxes to ignore leading and trailing blanks.
    3. Internal change consolidating calls for F1 help as listed at end of unit.

v0.20
  1. Correct error in loading Texture 3 that gave a divide by zero error if
     the specified longitude range was 0..360 deg.
  2. Add mouse option to display source image pixel location and intensity
     data in RGB and HSV systems.
  3. Incorporate JimsGraph code into main unit.  Make main LTVT image resizable.
     If the image area is non-square the Zoom refers to the number of image
     widths needed to span the lunar diameter.
  4. Add DEM button to main window which permits simulations based on Kaguya
     PDS-format (*.IMG) DEM files.  The file and drawing options are specfied 
     in a new DEM Options menu.
  5. Add Radius box to GoTo form, visible only when drawing simulations in 3D,
     that allows plotting of projected positions above or below IAU sphere.
  6. Change SAVE image annotations to include program version number, gamma value
     (if not = 1) and DEM grid step multiplier (if not = 1).

  v0.20.1
    1. Internal change: move TPolarCoordinates, PolarToVector, VectorToPolar 
       and ComputeDistanceAndBearing definitions from MoonPosition unit to 
       MPVectors unit.
    2. In libration tabulator listings, add "Percent Illumination" and "Libration"
       (amount by which center distance at zero libration exceeds current center
       distance of feature).  Also list center distance of feature at zero libration
       and option to select events based on minimum libration as an alternative to 
       maximum center distance.
    3. Supress mouse readout when a 3D simulation is being displayed and mouse 
       point is outside the rendered area.  
    4. Modify right-click GoTo function for 3D DEM display so that it picks up 
       the longitude, latitude and height data from the DEM (if on lunar disk), 
       rather than inferring it from the 2D projection.  If not on disk, shows
       GoTo form with current X-Y mouse position.
    5. Correct 3D DEM rendering steps so that it includes grid and mark center 
       options when requested.

  v0.20.2
    1. Add DEM options to render brightness with alternatives to Lambert's law
       (default, brightness determined by Sun's angle of incidence on surface).  
       Alternatives are Lommel-Seeliger law (no variation with surface tilt at 
       Full Moon phase) and "Lunar-Lambert" model of McEwen (weighted mix of 
       pure Lommel-Seeliger at Full phase to pure Lambertian at 104, or more, 
       from Full).
    2. Add libration circle (90 longitude great circle) to DEM renderings 
       if requested (under Cartographic Options).

                                                                    21 Jan 2010
